1. Field of the Invention
The invention relates to a method of crosscutting a web and stacking the cut sheets on a sheet stack, wherein the web being continuously fed to the crosscutter is decelerated, in particular to a standstill, at the cutting point for the duration of the cutting operation and after the cut the new head end of the web is caused to overlap the tail end of the cut sheet on the conveying path to the sheet stack.
The invention further relates to an impact-type crosscutter for webs comprising conveying means preceding and following the impact cutter, which after the cut cause the new head end of the web to overlap the tail end of the cut sheet and transport the latter to a sheet stack.
2. Discussion of Prior Art
Impact-type crosscutters have the advantage over rotary crosscutters that they are able to stack the sheets directly downstream of the impact cutter, that is to say, the sheet, which is immobilized during the cut, need not again be accelerated.
This, however, poses difficulties whith large-size sheets, and especially with those used in the electrical-insulation industry. Since the sheet must be slid across the stack, the resulting friction produces an electrostatic charge, so that even with a blown-in air cushion and the stack positioned obliquely, the sheet to be deposited is pulled along the upper sheets of the stack. As a result, as the height of the stack increases, the sheet slides less and less readily. Especially in the case of long sheets, this may make it impossible to deposit the sheet by sliding it forward on the stack. The electrostatic charge then is so great that it cancels out the lubricating effect of the air cushion, and sliding the sheet forward to lay it down or to straighten it for formation of a straight-edged stack then is difficult or impossible.
Difficulties of this type are not encountered with rotary crosscutters, where the sheet is moved to the stack by means of floating bars. However, rotary crosscutters entail much greater complexity of construction for overlapping the sheets and for decelerating them to a speed permitting satisfactory stacking of the sheets. In addition, rotary crosscutters are not suited for cutting all materials. Some materials are so brittle that they can be cut without fraying at the cut edge only with impact cutters.